Soft start clutch

ABSTRACT

A clutch provides two pairs of friction faces between rotatable input and output hubs. One of said hubs provides a coaxial cylindrical surface for support of the other hub and a neutral hub between a pair of radially outwardly extending shoulders providing its friction faces. The other hub, and the neutral hub are rotatably supported on the cylindrical surface between the shoulders with spring means associated with one of the friction faces urging the hubs together and the friction faces into contact with one another. A ring which is wedge shaped in radial cross sections and capable of being pressed inwardly lies preferably in a wedge shaped groove between said other hub and neutral hub. A helical spring surrounds the outer face of the ring and when wrapped down urges the ring inwardly to urge the block and hub apart and their respective clutch faces into the opposed clutch faces of the other hubs with sufficient force to permit transmission of torque.

Q United States Patent 51 3,642,106

Baer 1 Feb. 15 1972 [54] SOFT START CLUTCH Primary Examiner-Allan Drl-lerrmann [72] Inventor: John 8. Ba", Medford Lakes, NJ Attorney-Wolfe,Hubbard, Leydig, Voit & Osann, Ltd.

[73] Assignee: Warner Electric Brake & Clutch Com- ABSTRACT pan)" SouthBekm A clutch provides two pairs of friction faces between rotatable[22] Fil d; J l 22, 1970 input and output hubs. One of said hubsprovides a coaxial cylindrical surface for support of the other hub anda neutral [21] APPI' N05 572172 hub between a pair of radially outwardlyextending shoulders providing its friction faces. The other hub, and theneutral hub 52 us. Cl. ..192/70, 192/26, l92/84 c are wmbly PR i lsurface P 51 1 Int. Cl ....Fl6d 13/32, Fl 6d 27/10 i f g z h u 84 7 acesurging e u s toge er an e nctlon aces into con- [58] Field of Sean192/26 C 84 T 70 tact with one another. A ring which is wedge shaped inradial cross sections and capable of being pressed inwardly lies [56]References Cited' preferably in a wedge shaped groove between said otherhub UNITED STATES PATENTS and neutral hub. A helical spring surroundsthe outer face of R the ring and when wrapped down urges the ringinwardly to 25,229 8/1962 Sacchrnr et al 192/26 X urge the block and hubapart and their respective dutch faces 3,149,705 9/ 1964 h w into theopposed clutch faces of the other hubs with sufficient 2:3 et 192/84 T xforce to permit transmission of torque.

22 Claims, 7 Drawing Figures l 56 I 6a Q 5 I I ri S i f 44 4 22 /r// V,L r 56 .8 5a A 56 I ii I 24 \l\ I i" /6 r I /6 [c3 I I 45 I I t 45 i li [6 PATENTEDFEB 15 m2 3.642.106

SHEET 1 OF 2 mvcm'onz JOHN S. BAER A YS PATENTEUFEB 1 5 I972 SHEET 2 [1F2 mvcmoa'. JOHN S. B AER ATT S SOFT START CLUTCH This invention relatesto a clutch which although a friction face clutch is capable of softstarts. More specifically, it relates to a clutch which has a helicalspring actuator acting on a ringshaped wedge between a pair of rotatablehubs each of which carries clutch faces. The ring wedge segments whensqueezed inwardly force the hubs apart to cause them to engagerespective ones of a pair of opposed clutch faces on the other hub withsufficient force to permit the transfer of torque between the faces.

By use of light spring pressure, which presets the friction surfacesinto slight engagement, there is developed a tendency to resist turningon the part of the nondriven output hub, and this, in turn, will tend tocause the helical spring to wrap down tighter, which will cause theresistance to increase, etc.

More specifically, in accordance with the present invention, rotatableinput and output hubs are provided wherein one of those hubs provides acylindrical bearing surface for the other extending between a pair ofopposed shoulders providing opposed friction clutch surfaces. The otherhub and a neutral hub are rotatably supported together on the one hubbetween the shoulders and friction facesopposing those of the one hub.Very little clearance is provided between the hubs and spring urging atone of the friction faces of said one hub preferably keep all hubs andfriction faces in contact. Between the hub and the neutral hub is a ringwedge which when pressed at its outer surface'the friction clutchsurfaces into torque-transmitting engagement.

In accordance with the present invention the clutch may be a normallyengaged type which employs a spring which is normally wrapped down sothat release of the spring will disengage the ring wedge and the clutch.On the other hand, it is also possible to provide a normally disengagedclutch having a helical spring which is normally out of engagement withthe ring wedge and which causes engagement when wrapped down on the ringwedge.

For a better understanding of the present invention, reference is madeto the accompanying drawings in which,

FIG. 1 is an end view of a preferred embodiment of normally disengagedclutch;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1 showing theclutch in engaged condition;

FIG. 3 is a sectional view taken along line 33 of FIG. 2;

FIG. 4 is a partial sectional view similar to FIG. 2 showing the clutchin its normally disengaged condition;

FIG. 5 is a sectional view taken along line 55 of FIG. 2;

FIG. 6 is an axial sectional view of a modified clutch in accordancewith the present invention, which is normally engaged;

FIG. 7 is a sectional view taken along line 7-7 of the clutch of FIG. 6.

Considering first the clutch of FIGS. l5, reference is particularlydrawn to FIG. 2. In this particular clutch the output is taken along theshaft 10, whereas the input is applied to pulley 12 by a belt, such asan automobile fan belt, but it will be understood that within the scopeof the invention the inputs and outputs could easily be reversed. Inthis particular embodiment, the output hub 14 is a tubular structurehaving a uniform inner diameter, but having portions of different outerdiameter. The output hub 14 is connected to the shaft by setscrews 30,or other appropriate means. The intermediate section of the output hubhas a smooth cylindrical outer surface 16 intended to serve as a bearingfor the input and neutral hubs and terminated at one end by an enlargeddiameter portion which provides a shoulder 18 which serves a functionwhich will be later explained. Its other end 20 is threaded to receive anut-like member 22 which provides a shoulder or face 24 which is opposedto and spaced from shoulder 18. Effectively then, the output hub has abearing surface 16 between opposed shoulders 18 and 24. The shoulders insome other embodiment might themselves serve as the planar frictionclutch surfaces, but in this particular embodiment they do not. Rather,shoulder 18 is faced with an annular friction disc 26 and shoulder 24, asimilar friction disc 28, which provides the actual friction faces.

Between the shoulders 18 and 24 and their associated friction members 26and 28, are located a pair of hubs 32 and 34. In this particular casethe hub 32 is the driven input hub. These hubs have little lateralclearance but are laterally slidable on cylindrical surface 16 betweenthe friction members 26 and 28. Furthermore, the hubs 32 and 34 andfriction members 26 and 28 are urged together laterally by springs whichin this case are located in three bores parallel to the axis spacedaround shoulder 24 of nut 22. The spring means in this case are helicalsprings which bear against balls 38-which actually apply the axialpressure to the friction ring 28. The lateral clearances in the hubs 32and 34 and frictional members 26 and 28 have to be less than thediameter of the ball 38 to prevent loss of the balls. Adjustment ofclearances is accomplished by adjustment of the position of nut 22 onthe threaded portion 20 of output hub 16. When the position of nut 22 isfinally selected a setscrew 40 fixes the nutin position. Adjustment ofthe force applied by spring means 36 can be achieved through adjustmentscrews 42, one of which is provided in connection with each of the threesprings 36, as seen in FIG. 3. Other means of maintaining pressure onthe input and neutral hubs may be substituted between the nut 22 andfriction washer 28, or elsewhere, to achieve the same result as thespring arrangement shown. Some of the possible substitutes, for example,are corrugated Bellville washers, wave washers.

The hubs 32 and 34 are cut away between the two hubs to provide awedge-shaped groove to receive a ring wedge 44. As best seen in FIG. 5,ring wedge 44 is preferably composed of three identical segments 46,which are slightly spaced apart at their ends to permit radially inwardmovement of the wedge segments 46. While it is not preferred a highlyresilient onepiece structure might serve the purpose in someapplications. Ordinarily, however, the wedge ring is divided into threeor more segments. The ring wedge segments as they are moved radiallyinwardly serve to spread the hubs 32 and 34 further apart and therebysupply sufficient lateral force at the friction clutch faces to transmittorque from the input to output hubs. The faces of the input and neutralhubs adjacent the friction rings 26 and 28, respectively, serve as thefriction clutch faces for those elements.

Radially inward force to move the ring wedge segments 46 to actuate theclutch is provided by the spring 48. Spring 48 is normally out ofengagement with the outer periphery of the wedge segments, as shown inFIG. 4. Spring 48 is fixed to the neutral hub 34 by a press fit underinwardly projecting ridge 50a within tubular cover 50 which, in turn, isfixed to he neutral hub. Cover 50 is spaced from and surrounds thoseareas of input and neutral hubs 32 and 34 covered by spring 48 andserves to prevent the outward expansion of spring 48 to its completelyrelaxed position, thereby keeping the spring more stable and undergreater control. Spring 48 is a righthand helically wound spring, butthe last turn remote from the turn affixed to hub 34 by ridge 50a is aflat turn 480, which lies generally in a plane parallel to the axis.Conversion from the helical to flat turn is accomplished by an offset48b in the spring. The spring is composed of spring steel or otherselected magnetic material and is close spaced to a reluctance gap 52 atthe general radius spring. The reluctance gap is part of the magneticcircuit including radially extending flange 54 and web 56 formed ofsheet steel .or other magnetic material integrally as a part of the fanbelt pulley 58. Staked to the hub 32 is a planar sheetmetal aluminumring 60 which, in turn, is rivited by rivets 62 to the web 56 to supportthe pulley and in the process create the airgap 52. The magnetic fieldis created by a winding 64, which is supported from the nonrotatingframe in an annular channel 66 by brackets 68, as seen in FIG. 1. Themagnetic circuit of channel 66 is continued through web 56 and flange 54across airgap 52. Energizing the winding 64 creates a magnetic fieldwhich draws the turn 48a into the airgap 52 and tends to hold it inplace against the flange 54 as hub 32 rotates. As turn 48a rotates withthe input hub it wraps spring 48 down from the position shown in FIG. 4to the position shown in FIG. 2. In the course of this action thesegments 46 of the ring wedge 44 are forced radially inwardly betweenthe hubs 32 and 34 wedging them apart, as the consequence of which thesehubs are displaced and placed under lateral pressure until the opposedfriction faces effectively become one and are capable of transmittingtorque. Interestingly, engagement occurs gradually, or more accuratelysmoothly, because of the effect provided by the pressure of springs36'which maintain through the friction faces some slight resistanceinitially against the hubs turning, thereby causing the spring 48 totend to wrap down tighter on hubs 32 and 34. The effect is cumulative;as more resistance to rotating is experienced, the spring 44 tends towrap more tightly until the drive is completely positive. Clutchengagement will be smooth and produce soft starting rather than a suddengrab.

Referring now to FIGS. 6 and 7, a structure is shown which in manyrespects is similar to that of FIGS. 1-5. In this particular case outputshaft 78 is press fitted into tubular output hub 80, which in this casehas a pair of adjustable nut elements 82 and 84, both of which are heldin final selected position by a setscrew. A wedge shaped groove intowhich ring wedge 90 fits is provided between an input hub 86 and aneutral hub 88.

In this case ring wedge 90 is normally held in its inwardly urgedposition by spring 92 whose resilience holds it normally closed andwrapped down. In this particular case the spring is fixed at one end toneutral hub 88 by tang 92a and at the other end to a nylon collar 94 bytang 92b. In this case the spring action ordinarily holds the wedge inplace to urge the hubs 86 and 88 apart and into the friction members 96and 98, so that the clutch is engaged and the input and output hubsrotate as a unit. However, by moving a pawl 100 into the path of a stop102 on the nylon collar 94, the attached end of spring 92 through tang92b is stopped and as tang 92a continues to rotate will open up. Theforce is thus removed from the wedge segments 90 allowing pressure to beremoved from the friction members 96 and 98, and disengaging the clutch;thereupon the input hub 86 continues to rotate as it is driven, but theoutput hub is held stationary through the spring 92 by the stop 100which tends to unwind the spring 92 as rotation continues. Once the stop100 is withdrawn from the shoulder 102, however, the spring 92 due toits internal resilience again wraps down on the wedge 90 spreading hubs86 and 88 apart and forcing them into the friction members 96 and 98with sufficient force to transmit torque from the input to the output.In this case a wave washer 104 has been substituted for the spring means36 of FIG. 2 and functions in the same way but without the flexibilityin pressure adjustment. However it provides for a soft start as in theFIGS. l-S embodiment.

Two variations of the present invention have been described, and it willbe understood that these embodiments are merely representative ofvariations which are possible within the scope of the invention. Furthermodifications are possible, including variations of the structure shownand entirely modified embodiments. All such modifications within thescope of the claims are intended to be within the scope and spirit ofthe present invention.

I claim:

1. A friction clutch comprising a rotatable input hub having a frictionclutch face,

an output hub rotatable about the same axis of rotation as the inputhub,

a pair of hubs rotatable about the input hub axis of rotation andrelatively movable with respect to one another generally parallel tosaid axis of rotation, one of which has a generally cylindrical outerface and at least one of which is a neutral hub, neither input noroutput,

a ring wedge composed of a ring having radial cross sections in the formof an inwardly directed wedge, and an outer surface slightly larger thanthe cylindrical outer face of said at least one of said pair of hubs andlocated between said pair of hubs whereby pressure on the outer surfaceof the ring wedge will axially displace said pair of hubs relative toone another, and cause its friction clutch faces to engage, and

a helical spring surrounding said ring wedge, said helical spring beingattached at one end to one of said pair of hubs,

said spring when wound down being operable to wrap down on the ringwedge, thereby exerting the pressure on the ring wedge to urge said hubsapart and the clutch faces into engagement.

2. The friction clutch of claim 1 in which the ring wedge is dividedinto a plurality of segments.

3. The friction clutch of claim 2 in which the ring wedge is dividedinto three wedge segments.

4. The friction clutch of claim 1 in which the input hub is one of thepair of hubs.

5. Thefriction clutch of claim 4 in which the one end of the helicalclutch is fixed to the neutral hub and normally out of engagement withthe ring wedge and input hub.

6. The friction clutch of claim 5 in which the spring is composed ofmagnetic material and in which magnetic actuation means is employed toact upon the other end of the helical spring to cause it to wrap downinto engagement with the ring wedge.

7. The friction clutch of claim 6 in which the magnetic actuator meansis employed to cause the free end of the helical spring to bemagnetically drawn to and along with the input hub, thereby wrappingdown the helical spring on the ring wedge.

8. The friction clutch of claim 7 in which the magnetic means includesflux-generating winding and a magnetic circuit including a portion ofthe input hub, which includes an annular reluctance gap into which thelast turn of the helical winding is drawn.

9. The friction clutch of claim 1 in which one of the input and outputhubs consists of a body having a cylindrical support surface on whichthe pair of hubs is rotatably and slidably supported between a pair ofopposed outwardly extending radial shoulders on the output hub providingfriction clutch faces against which opposed faces on each of the pair ofhubs are forced by the wedging action of the ring wedge.

10. The friction clutch of claim 9 in which the output hub is the hubconsisting of the tubular support and the input hub is one of the pairof hubs.

1 l. The friction clutch of claim 1 in which at least one of thefriction clutch faces is a separate piece separated from and urged awayfrom its supporting structure by resilient means urging it laterally andtending to hold friction clutch surfaces into contact with one anotherat all times.

12. The friction clutch of claim 9 in which at lest one of the frictionclutch faces is a separate piece separated from and urged away from itssupporting structure by resilient means urging it laterally and tendingto hold friction clutch surfaces into contact with one another at alltimes.

13. The friction clutch of claim 1 in which the helical spring isnormally out of engagement by virtue of its internal resilience and isdrawn into engagement by the means selectively acting on the other end.

14. The friction clutch of claim 1 in which the pair of hubs includesthe input hub and in which the helical spring is normally in engagementby virtue of its internal resilience and has one end attached to theneutral hub and its other end attached to a collar bearing a stopshoulder which rotates with the engaged clutch, so that a stopinterposed in the path of the shoulder will stop the collar anddisengage the clutch.

15. A friction clutch comprising an output hub consisting of a bodyhaving a coaxial cylindrical surface and a pair of opposed outwardlyextending radial shoulders providing friction clutch faces,

an input hub rotatably supported on the cylindrical surface of theoutput hub between said shoulders and having a clutch face opposing oneof said shoulders,

a neutral hub positioned adjacent the input hub rotatably supported onthe cylindrical surface of the output hub and bearing a clutch faceopposing the other shoulder of the output hub,

the friction clutch faces is a separate piece separated from and urgedaway from its supporting structure by resilient means urging itlaterally and tending to hold friction clutch surfaces into contact withone another at all times a ring wedge positioned between the input huband the neutral hub and having a radial cross section in the form of aninwardly directed wedge,

a helical spring surrounding, but normally out of engagement with saidring wedge, and means causing said spring 5 to wrap down on said ringwedge to force the input and neutral hubs apart and their clutch facesinto engagement with the friction clutch faces of the output hub.

16. The friction clutch of claim in which at least one of 17. Thefriction clutch of claim 16 in which the resilient means urging theseparate piece is a plurality of springs 15 together with pressureelements distributed around the periphery of the face in recesses normalto the face.

18. The friction clutch of claim 17 in which the helical spring isattached to one end to said neutral hub and is arranged to be engaged bythe input hub to cause the clutch to become engaged.

19. The friction clutch of claim 18 in which the helical spring iscomposed of magnetic material and is wrapped down on the ring wedge bymagnetic means providing means for attracting the free end of the springto the input hub.

20. The friction clutch of claim 19 in which the magnetic means includesmagnetic circuit a portion of which is included in the input hub andincludes a reluctance gap into which the last turn of the spring isdrawn when the winding is energized.

21. The friction clutch of claim 15 in which at least one of the outputhub clutch surfaces is movable relative to the output hub in the axialdirection and spring means is provided to urge said friction surfaceinto contact with its opposed friction surface at all times.

22. The friction clutch of claim 21 in which said one of the output hubclutch surfaces is a ring subjected to spring pressure through aplurality of balls spring urged at a plurality of points around thecircumference of said ring.

1. A friction clutch comprising a rotatable input hub having a frictionclutch face, an output hub rotatable about the same axis of rotation asthe input hub, a pair of hubs rotatable about the input hub axis ofrotation and relatively movable with respect to one another generallyparallel to said axis of rotation, one of which has a generallycylindrical outer face and at least one of which is a neutral hub,neither input nor output, a ring wedge composed of a ring having radialcross sections in the form of an inwardly directed wedge, and an outersurface slightly larger than the cylindrical outer face of said at leastone of said pair of hubs and located between said pair of hubs wherebypressure on the outer surface of the ring wedge will axially displacesaid pair of hubs relative to one another, and cause its friction clutchfaces to engage, and a helical spring surrounding said ring wedge, saidhelical spring being attached at one end to one of said pair of hubs,said spring when wound down being operable to wrap down on the ringwedge, thereby exerting the pressure on the ring wedge to urge said hubsapart and the clutch faces into engagement.
 2. The friction clutch ofclaim 1 in which the ring wedge is divided into a plurality of segments.3. The friction clutch of claim 2 in which the ring wedge is dividedinto three wedge segments.
 4. The friction clutch of claim 1 in whichthe input hub is one of the pair of hubs.
 5. The friction clutch ofclaim 4 in which the one end of the helical clutch is fixed to theneutral hub and normally out of engagement with the ring wedge and inputhub.
 6. The friction clutch of claim 5 in which the spring is composedof magnetic material and in which magnetic actuation means is employedto act upon the other end of the helical spring to cause it to wrap downinto engagement with the ring wedge.
 7. The friction clutch of claim 6in which the magnetic actuator means is employed to cause the free endof the helical spring to be magnetically drawn to and along with theinput hub, thereby wrapping down the helical spring on the ring wedge.8. The friction clutch of claim 7 in which the magnetic means includesflux-generating winding and a magnetic circuit including a portion ofthe input hub, which includes an annular reluctance gap into which thelast turn of the helical windiNg is drawn.
 9. The friction clutch ofclaim 1 in which one of the input and output hubs consists of a bodyhaving a cylindrical support surface on which the pair of hubs isrotatably and slidably supported between a pair of opposed outwardlyextending radial shoulders on the output hub providing friction clutchfaces against which opposed faces on each of the pair of hubs are forcedby the wedging action of the ring wedge.
 10. The friction clutch ofclaim 9 in which the output hub is the hub consisting of the tubularsupport and the input hub is one of the pair of hubs.
 11. The frictionclutch of claim 1 in which at least one of the friction clutch faces isa separate piece separated from and urged away from its supportingstructure by resilient means urging it laterally and tending to holdfriction clutch surfaces into contact with one another at all times. 12.The friction clutch of claim 9 in which at lest one of the frictionclutch faces is a separate piece separated from and urged away from itssupporting structure by resilient means urging it laterally and tendingto hold friction clutch surfaces into contact with one another at alltimes.
 13. The friction clutch of claim 1 in which the helical spring isnormally out of engagement by virtue of its internal resilience and isdrawn into engagement by the means selectively acting on the other end.14. The friction clutch of claim 1 in which the pair of hubs includesthe input hub and in which the helical spring is normally in engagementby virtue of its internal resilience and has one end attached to theneutral hub and its other end attached to a collar bearing a stopshoulder which rotates with the engaged clutch, so that a stopinterposed in the path of the shoulder will stop the collar anddisengage the clutch.
 15. A friction clutch comprising an output hubconsisting of a body having a coaxial cylindrical surface and a pair ofopposed outwardly extending radial shoulders providing friction clutchfaces, an input hub rotatably supported on the cylindrical surface ofthe output hub between said shoulders and having a clutch face opposingone of said shoulders, a neutral hub positioned adjacent the input hubrotatably supported on the cylindrical surface of the output hub andbearing a clutch face opposing the other shoulder of the output hub, aring wedge positioned between the input hub and the neutral hub andhaving a radial cross section in the form of an inwardly directed wedge,a helical spring surrounding, but normally out of engagement with saidring wedge, and means causing said spring to wrap down on said ringwedge to force the input and neutral hubs apart and their clutch facesinto engagement with the friction clutch faces of the output hub. 16.The friction clutch of claim 15 in which at least one of the frictionclutch faces is a separate piece separated from and urged away from itssupporting structure by resilient means urging it laterally and tendingto hold friction clutch surfaces into contact with one another at alltimes.
 17. The friction clutch of claim 16 in which the resilient meansurging the separate piece is a plurality of springs together withpressure elements distributed around the periphery of the face inrecesses normal to the face.
 18. The friction clutch of claim 17 inwhich the helical spring is attached to one end to said neutral hub andis arranged to be engaged by the input hub to cause the clutch to becomeengaged.
 19. The friction clutch of claim 18 in which the helical springis composed of magnetic material and is wrapped down on the ring wedgeby magnetic means providing means for attracting the free end of thespring to the input hub.
 20. The friction clutch of claim 19 in whichthe magnetic means includes magnetic circuit a portion of which isincluded in the input hub and includes a reluctance gap into which thelast turn of the spring is drawn when the winding is energized.
 21. Thefriction clutch of cLaim 15 in which at least one of the output hubclutch surfaces is movable relative to the output hub in the axialdirection and spring means is provided to urge said friction surfaceinto contact with its opposed friction surface at all times.
 22. Thefriction clutch of claim 21 in which said one of the output hub clutchsurfaces is a ring subjected to spring pressure through a plurality ofballs spring urged at a plurality of points around the circumference ofsaid ring.